Geiger counter



F. P. SMITH GEIGER COUNTER Nov. 15, 1960 Filed May 13, 1957 AUD/O AMPLIFIER GEIGER COUNTER Frank Patterson Smith, Fort Wayne, Ind., assignor to International Telephone and Telegraph Corporation Filed May 13, 1957, Ser. No. 658,594

Claims. c1. 250-83.6)

The present invention relates to a Geiger counter, and more particularly to a unique power supply for supplying high voltage to the Geiger tube.

Conventional Geiger counters used for prospecting are portable, usually being carried by a prospector as he walks over the terrain. Such portable counters contain the usual battery power supplies, circuit components and speaker, all of which must be carried by the individual. Since the equipment is carried by the individual, it is desirable that it possess a minimum of weight and be as small as possible.

The present invention is unique in the respect that it eliminates certain of the high voltage power supply components thereby reducing the weight and size of the equipment.

It is therefore an object of this invention to provide a Geiger counter which requires fewer parts, is less costly, and easier to use than conventional equipment.

It is another object of this invention to provide-a Geiger counter which requires only a single low voltage power supply for operating the Geiger tube as well as the associated circuitry.

It is still another object of this invention to provide a- Geiger counter wherein the high voltage power supply comprises essentially only a condenser in combination with a unidirectionally conductive device.

In accordance with this invention there is provided a Geiger counter comprising a Geiger tube, means for amplifying the pulses generated by the Geiger tube, a voltage step-up transformer having an input winding coupled to said amplifying means and an output winding, a unidirectionally conducting device coupled to said output winding, and a storage condense-r coupled to said unidirectionally conducting device and across the Geiger tube, whereby the power for operating the Geiger tube is derived from said storage condenser.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of two embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a schematic diagram of one embodiment of this invention; and

Fig. 2 is a schematic diagram, in part, of a second embodiment.

Referring to the drawings, an audio amplifier (either a semiconductor or vacuum tube) generally indicated by the reference numeral 1 of conventional circuit configuration may include a normally non-conductive amplifier 2 operatively coupled to a normally conductive amplifier 3. A transformer 4 having primary and secondary windings 5 and 6, respectively, is coupled to the amplifier 3, the upper end 7 of the primary winding being connected to the amplifier anode 8. The low voltage power supply for the amplifier 3 is connected to suitable terminals 9 leading to a tap 10 on the primary winding 5 intermediate the ends thereof. The exact position of the tap 10, of

States Patent 0 ice course, will depend upon the turns ratio of the transformer, the value of the supply voltage, the type of amplifier 3, as well as the other usual circuit parameters, in order to achieve the operation which will be explained in the following.

The lower end 11 of the primary winding is connected to a unidirectionally conducting device 12 which may consist of the usual diode tube or crystal. In the drawing, the winding end 11 is connected to the cathode 13 of the tube 12, the anode 14 being connected to a condenser 15 grounded as shown.

A conventional Geiger tube or electron discharge device which is responsive to gamma-radiation and the like is indicated by the numeral 16 and has one electrode 17 grounded and the other electrode 18 coupled to a resistor 19 which is also connected to the anode 14 of the diode 12. The electrode 18 is also connected to a condenser 20 which in turn is grounded through a resistor 21. This condenser 20 and 21 serve as a time constant network which is operatively coupled by circuit connection 22 to the control grid 23 of the amplifier 2. As will appear from the following description, the time constant network 20, 21 provides a discharge time which falls within that of the audio frequency spectrum. Preferably, a voltage regulator 31 of some type, such as one or more neon tubes connected in series, is coupled across the condenser 15 to limit pulse height, as will become apparent from the following.

In operation, the low voltage power supply for operating the amplifier 1 is coupled to the supply terminals 9. The amplifier 3 is biased such that it is normally conductive but is rendered non-conductive upon receiving a negativegoing pulse on the control grid 24. The amplifier 2 is biased to be normally nonconductive but is rendered conductive upon the application of a positive-going pulse to the grid 23.

With an initial charge on the condenser 15, gammaradiation or the like falling on the Geiger tube 16 will produce a current discharge therethrough, which is supplied by the condenser 15. A positive-going pulse 25 is thereupon produced, which pulse contains audio com- 7 ponents as determined by the time constant network 20, 21.

This pulse 25 causes the amplifier 2 momentarily to conduct heavily, thereby producing a corresponding reduction in anode voltage as indicated by the pulse waveform 26. This pulse 26 momentarily biases the amplifier 3 to rapid cutoflf, causing the magnetic field in the transformer 4 to collapse thereby producing a relatively large negative voltage pulse 27 which is impressed on the cathode 13 of the diode 12. The diode then conducts and charges the condenser 15. With the condenser 15 thus charged, radiation falling on the Geiger tube 16 will again discharge the condenser causing the generation of another pulse 25, which pulse serves in recharging the condenser 15. Thus, the condenser 15 serves as the power supply for the Geiger tube 16 thereby eliminating the need for a vibrator power supply as conventionally used for generating the high voltage needed to operate the Geiger tube.

Circuit parameters must be such that the overall circuit gain is adequate to maintain a charge on capacitor 15 of sufficient magnitude to operate the Geiger tube in the presence of only minimum background level radiation count.

Any suitable means may be used for initially charging the condenser 15, one preferred method being the moment-ary opening of switch 28 after the amplifier has been operating long enough to establish normal current through the transformer. Other starting means may be employed, such as the insertion of noise in the line 22.

A suitable speaker 29 is coupled across the transformer secondary 6 to reproduce audibly the pulses which emanate from the Geiger tube 16.

In Fig. 2 is illustrated an alternative embodiment of this invention wherein the transformer is provided with an input or low voltage winding 29 and an output or high voltage winding 30. The operation of the circuit is the same as that illustrated in Fig. 1. The terminal connections of the winding 30 to the diode 12 may be reversed in order to secure proper polarity of the output pulses which are coupled to the diode.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention.

What is claimed is:

1. Radiation-sensitive circuitry comprising a Geiger tube having two terminals, one of said terminals being grounded, a normally nonconductive first amplifier having a control grid and an anode, a time constant network composed of a condenser and a resistor, said resistor being connected between said control grid and ground, said condenser being connected between said control grid and the other terminal of said Geiger tube, a normally conductive second amplifier having a control grid and an anode, a coupling capacitor coupled between said first amplifier anode and the second amplifier control grid, a transformer having primary and secondary windings, one side of the primary Winding being con nected to the second amplifier anode, a diode having cathode and anode elements, the diode cathode being connected to the other side of said primary winding, a charging capacitor connected between the diode anode and ground, and a connection between said diode anode and the other of said Geiger tube terminals.

2. Radiation-sensitive circuitry comprising a Geiger tube having two terminals, one of said terminals being grounded, a normally nonconductive first amplifier having a control grid and an anode, a time constant network composed of a condenser and a resistor, said resistor being connected between said control grid and ground, said condenser being connected between said control grid and the other terminal of said Geiger tube, a normally conductive second amplifier having a control grid and an anode, a coupling capacitor coupled between said first amplifier anode and the second amplifier control grid, a transformer having primary and secondary windings, a B supply tap on said primary winding between the sides thereof, one side of the primary winding being connected to the second amplifier anode, a diode having cathode and anode elements, the diode cathode being connected.

to the other side of said primary winding, a charging capacitor connected between the diode anode and ground, and a connection between said diode anode and the other of said Geiger tube terminals.

3. Radiation-sensitive circuitry comprising a Geiger tube having two terminals, one of said terminals being grounded, a normally nonconductive first amplifier having a control grid and an anode, a time constant network composed of a condenser and a resistor, said resistor being connected between said control grid and ground, said condenser being connected between said control grid and the other terminal of said Geiger tube,

a normally conductive second amplifier having a control grid and an anode, a coupling capacitor coupled between said first amplifier anode and the second amplifier control grid, a transformer having primary and secondary windings, one side of the primary winding being connected to the second amplifier anode, a diode having cathode and anode elements, the diode cathode being connected to the other side of said primary winding, a charging capacitor connected between the diode anode and ground, a connection between said diode anode and the other of said Geiger tube terminals, and a speaker coupled across said secondary winding.

4. Radiation-sensitive circuitry comprising a Geiger tube having two terminals, one of said terminals being grounded, a normally nonconductive first amplifier having a control grid and an anode, a time constant network composed of a condenser and a resistor, said resistor being connected between said control grid and ground, said condenser being connected between said control grid and the other terminal of said Geiger tube, a normally conductive second amplifier having a control grid and an anode, a coupling capacitor coupled between said first amplifier anode and the second amplifier control grid, a transformer having primary and secondary windings, one side of the primary winding being connected to the second amplifier anode, a diode having cathode and anode elements, one of said diode elements being connected to the other side of said primary winding, a charging capacitor connected between the other diode element and ground, and a connection between said other diode element and the other of said Geiger tube terminals.

5. Radiation-sensitive circuitry comprising a Geiger tube, a normally nonconductive first amplifier having a first control element and a first output circuit for supplying a signal voltage, a time constant network coupled across said Geiger tube and to said control element, a normally conductive second amplifier having a second control element and a second output circuit, said second control element coupled to said first output circuit and responsive to said signal voltage to render said second amplifier nonconductive, a transformer having primary and secondary windings, one side of said primary winding being coupled to said second output circuit, a diode having cathode and anode elements, one of said diode elements being coupled to the other side of said primary winding, the other of said diode elements being coupled to a source of reference voltage, and a charging capacitor having two terminals, one of said terminals being coupled to one of said diode elements, said capacitor being coupled across said Geiger tube whereby conduction by said Geirger tube serves to at least partially discharge said capacitor.

References Cited in the file of this patent UNITED STATES PATENTS 

